A solar water heater system is a type of fluid heating system that typically has two primary components. The first component is a solar panel, possibly comprising a plurality of evacuated tubes and a heat-insulated reservoir for temporarily storing heated fluid to be transferred, for heating water using solar energy. The second component is a storage tank for storing the heated water. It is common to situate the storage tank above the panel so that the heated water, which tends to rise, naturally accumulates within the storage tank without the use of a pump. However, this arrangement may be disadvantageous in various respects. Firstly, because the storage tank can be heavy, situating the tank above the panel may cause the system to be top-heavy and therefore unstable, e.g. in high winds. Secondly, the tank may be considered unsightly.
In view of these disadvantages, some solar water heating systems have been developed wherein the storage tank is situated lower than the solar panel. This is typically achieved through the use of an electrical pump that circulates the water through hoses or pipes between the panel and the storage tank. Such systems are disadvantageous in that the pump consumes external power (i.e. electricity) and requires a control system, which may increase equipment, installation and operating costs.
Some solar water heater systems employ two types of liquid—a primary liquid and a secondary liquid—which are kept in isolation from one another. The primary liquid is the water that is heated within the system, e.g. for human consumption. The secondary liquid is another liquid which is heated within the solar panel and whose heat is conveyed to the primary liquid by way of a heat exchanger. The secondary liquid typically has a freezing point that is lower than that of water. This is in order to limit the risk of freezing damage to the panel in colder climates. The secondary liquid may for example by ethylene glycol or an ethanol solution as used in conventional automotive windshield washer fluid. The heat exchanger is used to convey heat from the secondary liquid to the primary liquid without fluid communication between them. The heat exchanger is contained within the primary liquid storage tank. In such tanks, any vibration of the heat exchanger during its use may jeopardize the structural integrity of the tank, risking a leak. Moreover, known liquid storage tanks of this type are typically intended for installation in a predetermined orientation, which may be unsuitable for certain consumers.
A pump for heated liquid that operates without the use of external power would be desirable. As well, a fluid heating and storage tank that is capable of better withstanding vibration and that may be capable of installation in more than one orientation would be desirable. Finally, a fluid heating system employing either or both of such components would be desirable.